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# Important Questions and Answers: Assembly of Parts

Mechanical - Computer Aided Design - Assembly of Parts

ASSEMBLY OF PARTS

1.       Define Assembly modeling.

Assembly modeling is defined as a technology and method used by computer-aided design and product visualization computer software systems to handle multiple files that represent components within a product. The components within an assembly are represented as solid or surface models.

2.       Write short note on Exploded view.

An exploded view consists of series of steps. One can create steps by selecting and dragging parts in graphical area.

Example – Exploded view of Assembly of Pulley block

3.    List Features of Bottom-up assembly approach.

Allows the designer to use part drawings that already exist (off the shelf)

Provides the designer with more control over individual parts

Multiple copies (instances) of parts can be inserted into the assembly

4.           List Features of Top-down assembly approach.

The approach is ideal for large assemblies consisting of thousands of parts.

The approach is used to deal with large designs including multiple design teams.

It lends itself well to the conceptual design phase

E.g. :

Piping and fittings

Welds

Lock pins

5.           List advanced Mating conditions in assembling modeling.

6.     Applications of Assembly Models Interference checking Visualization

Rendered

Exploded

Animation

Mechanism analysis

7.        Assembly sequence affects

difficulty of assembly steps

need for fixture

potential for parts damage during assembly and part mating

ability to do in-process testing

occurrence of the need for reworking

time of assembly

assembly skill level

unit cost of assembly

8.        Interference fit

Fits is clearance fit

tight fits is interference fit

Coplanar: two normal vectors are parallel

‘Coplanar’ complements ‘against’

9.        Sketch the Precedence Diagram.

Designed to show all the possible assembly sequences of a product.

Each individual assembly operation is assigned a number.

Diagram is usually organized into columns

10.   What are the three terms used in limit system?

1.     Tolerance: Deviation from a basic value is defined as Tolerance. It can be obtained by taking the difference between the maximum and minimum permissible limits.

2.     Limits: Two extreme permissible sizes between which the actual size is contained are defined as limits.

3.     Deviation: The algebraic difference between a size and its corresponding basic size. There are two types of deviations: 1) Upper deviation 2) Lower deviation

11.   Write short note on Tolerances.

Due to human errors, machine settings, etc., it is nearly impossible to manufacture an absolute dimension as specified by the designer. Deviation in dimensions from the basic value always arises. This deviation of dimensions from the basic value is known as Tolerance.

12.  Define Clearance fit.

Clearance fit is defined as a clearance between mating parts. In clearance fit, there is always a positive clearance between the hole and shaft.

13.  Why Transition fit occurs?

Transition fit may result in either an interference or clearance, depending upon the actual values of the tolerance of individual parts.

14.  When Interference fit is obtained?

Interference fit is obtained if the difference between the hole and shaft sizes is negative before assembly. Interference fit generally ranges from minimum to maximum interference. The two extreme cases of interference are as follows:

15.      What is called Minimum interference?

The magnitude of the difference (negative) between the maximum size of the hole and the minimum size of the shaft in an interference fit before assembly.

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